Xceptional species diversity of Hoplitomeryx even since its first record, with the occurrence of three different forms in the oldest localities of Gargano (Supplementary Table S1) and scores that range from 0 to 0.5, this latter being the highest score recorded among the fossil sample (Fig. 4A). Such differences reveal the existence of differential resource utilization and niche segregation for the various species studied, with Hoplitomeryx sp.2 and Hoplitomeryx sp.3 being more dependent on soft foods and Hoplitomeryx sp.4 already having a comparatively higher proportion of tough abrasive elements (similar to the browse-dominated mixed feeder T. imberbis31) or incorporating some exogenous grit into its diet. Although only a few specimens have been found in biozone 1, this pattern reveals that Hoplitomeryx did not undergo uniform diversification dynamics after invading Gargano, but instead a prodigious adaptive radiation characterized by an accelerated accumulation of species, concomitant with an early burst of phenotypic and MS023 dose ecological diversity. The first co-occurrence of all Hoplitomeryx species is registered in biozone 2 (Fig. 4A), which corroborates that the genus diversified rapidly. It is worth noting, however, that the ecological diversity of the species starts to decline at this time, as denoted by a decrease of the wear scores and their GW 4064 site restriction to a rather narrower range of diet composition. This trend culminates in biozone 3 (e.g., Chiro 5A and Chiro 27), in where all species occurred with very low scores (MS = 0) in a soft-leafy browsing niche. It is important to stress that all these species exhibited a higher level of abrasion in biozone 2. Among extant ungulates, there are only browser species with scores lower than 0.2, which indicates a very attritive diet probably based on leaves and twigs for the species in biozone 2 and 3 which did not contribute to dietary abrasion in any appreciable way, with scarce or even no abrasive foods selected. The high abundance of very soft food items in this stage apparently allowed selective foraging in all the species to consume not the entire plant but the most succulent and nutritious (i.e., high energy-yielding) plant parts (e.g., selecting leaves over stem, or selecting the shrub with the larger leaves or thickest twigs, etc)37. One implication of this is that Hoplitomeryx would undergo a rapid increase in population density that, in tandem with the lack of natural predators and food competitors in Gargano19, might have caused a decline in mortalityScientific RepoRts | 6:29803 | DOI: 10.1038/srepwww.nature.com/scientificreports/Figure 4. Causes and trajectories of adaptive radiations. (A) Evolutionary history of the diet of Hoplitomeryx species traced according to chronological sequence of the biozones. (B) Evolution of body size through time. (C) Evolution of the wear pattern of the most widespread species and correlation with main changes in the micromammal association. The figure was designed through Adobe Photoshop CS3 software. rates and a phase of overpopulation in biozone 3. As observed in small islands4,5,38,39, such a lack of control of the population growth rate has led to a degradation of the preferred vegetation in Gargano and increased intraspecific competition for these food resources. A trend towards increased mesowear values followed by a new burst in ecological diversification is observed after biozone 3, as reflected especially by the small-sized Hoplitomeryx sp.Xceptional species diversity of Hoplitomeryx even since its first record, with the occurrence of three different forms in the oldest localities of Gargano (Supplementary Table S1) and scores that range from 0 to 0.5, this latter being the highest score recorded among the fossil sample (Fig. 4A). Such differences reveal the existence of differential resource utilization and niche segregation for the various species studied, with Hoplitomeryx sp.2 and Hoplitomeryx sp.3 being more dependent on soft foods and Hoplitomeryx sp.4 already having a comparatively higher proportion of tough abrasive elements (similar to the browse-dominated mixed feeder T. imberbis31) or incorporating some exogenous grit into its diet. Although only a few specimens have been found in biozone 1, this pattern reveals that Hoplitomeryx did not undergo uniform diversification dynamics after invading Gargano, but instead a prodigious adaptive radiation characterized by an accelerated accumulation of species, concomitant with an early burst of phenotypic and ecological diversity. The first co-occurrence of all Hoplitomeryx species is registered in biozone 2 (Fig. 4A), which corroborates that the genus diversified rapidly. It is worth noting, however, that the ecological diversity of the species starts to decline at this time, as denoted by a decrease of the wear scores and their restriction to a rather narrower range of diet composition. This trend culminates in biozone 3 (e.g., Chiro 5A and Chiro 27), in where all species occurred with very low scores (MS = 0) in a soft-leafy browsing niche. It is important to stress that all these species exhibited a higher level of abrasion in biozone 2. Among extant ungulates, there are only browser species with scores lower than 0.2, which indicates a very attritive diet probably based on leaves and twigs for the species in biozone 2 and 3 which did not contribute to dietary abrasion in any appreciable way, with scarce or even no abrasive foods selected. The high abundance of very soft food items in this stage apparently allowed selective foraging in all the species to consume not the entire plant but the most succulent and nutritious (i.e., high energy-yielding) plant parts (e.g., selecting leaves over stem, or selecting the shrub with the larger leaves or thickest twigs, etc)37. One implication of this is that Hoplitomeryx would undergo a rapid increase in population density that, in tandem with the lack of natural predators and food competitors in Gargano19, might have caused a decline in mortalityScientific RepoRts | 6:29803 | DOI: 10.1038/srepwww.nature.com/scientificreports/Figure 4. Causes and trajectories of adaptive radiations. (A) Evolutionary history of the diet of Hoplitomeryx species traced according to chronological sequence of the biozones. (B) Evolution of body size through time. (C) Evolution of the wear pattern of the most widespread species and correlation with main changes in the micromammal association. The figure was designed through Adobe Photoshop CS3 software. rates and a phase of overpopulation in biozone 3. As observed in small islands4,5,38,39, such a lack of control of the population growth rate has led to a degradation of the preferred vegetation in Gargano and increased intraspecific competition for these food resources. A trend towards increased mesowear values followed by a new burst in ecological diversification is observed after biozone 3, as reflected especially by the small-sized Hoplitomeryx sp.
